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One Saturday several years ago, Sumit Mohan arrived at the hospital at Columbia University in New York City. Sumit is a nephrologist, which is a kidney doctor, and many of his patients are waiting for new kidneys. He was at the hospital to do rounds, which is a task he usually does with all the doctors who are involved in transplanting kidneys, and that includes surgeons. But on this particular Saturday, something strange was going on. 

Sumit MOHAN: So I had one particular weekend where I came in. Surgeon’s not to be found. Now, if you guys know surgeons they’re all early risers, like, you know, being in the hospital early. And so that was a surprise.

So Sumit asked around. “Hey, where is everyone? Where are all the surgeons?” It turns out, they were in the Operating Room. They were all doing transplant surgeries. So Sumit figured he and the medical team would just do the rounds by themselves without the surgeons and he’d update them on the next day, Sunday morning.

MOHAN: And instead what happens is they’re back in the operating room. It’s like, wait, did something go wrong earlier? They’re like no. Another patient, another transplant, and essentially, what happened over that weekend is our surgical team transplanted five kidneys. And I never saw them. And so the question in my mind was like, wait a minute. Why is our surgical team suddenly so busy?

Sumit was totally puzzled. Transplant centers normally do about 2 to 4 transplants per week. So why was his hospital performing so many surgeries on weekends? And did that spike happen at all transplant centers? 

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That question led to a journey, over several years, to a lot of other questions, including why thousands of patients on the kidney transplant list die each year before receiving a kidney and whether some of those deaths could’ve been avoided. We’re going to hear about that journey today and what a Nobel laureate in economics has to say about the way that we transplant organs in the U.S.

From the Freakonomics Radio Network, welcome to Freakonomics, M.D. 

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I’m Bapu Jena. I’m an economist but I’m also a medical doctor. And in each episode, I dissect fascinating questions at the sweet spot between health and economics. 

Today: More than 4,000 people die on the waitlist for a kidney transplant every year in the U.S. And thousands of kidneys from deceased donors are thrown away. Are usable kidneys from deceased donors going to waste? If so, why? And what can we do about it?

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Before we dive into what Sumit and his team discovered, let’s talk about kidneys, which by the way are amazing. These little bean-shaped organs — uh yeah, kidneys look like kidney beans — are less than five inches long, and they help remove waste from the body. Most of us have two kidneys, but they can falter for any number of reasons — like trauma, infections, diabetes, high blood pressure. Chronic kidney damage is often irreversible and it worsens over years, eventually, it turns into something that we call kidney failure. Currently, more than 700,000 Americans are affected by this condition. 

People with kidney failure often go on dialysis, which is an invasive process that basically has a machine do the kidney’s work. But dialysis is really expensive, and it requires multiple, long visits to a dialysis center each week, and over time it usually stops working. Only half of people on dialysis survive beyond three years. So, many people on dialysis also go onto the transplant waiting list to get a kidney from a living or deceased donor. 

One transplanted kidney can solve the problem of both kidneys failing. And that’s because the human body only needs one kidney.

And oh, by the way, there’s a great episode from Freakonomics Radio all about dialysis from earlier this year. That’s called “Is Dialysis a Test Case of Medicare for All? (Ep. 457)” We’ll put a link to it in the show notes. You should definitely give it a listen. 

But today on our show, we’re zooming in on kidney transplants. Transplants can be risky. Sometimes the patient’s body rejects the new organ, or the benefit doesn’t last for other reasons. But when it is successful? People with kidney failure who receive a new organ live an average of 11 years longer than those who die on the waiting list— that’s three times longer than someone on dialysis. For patients who are between the ages of 20 and 39, that difference actually climbs to 17 years. To put it simply, people with kidney failure who get a new organ usually live much longer than those stuck on dialysis. Here’s Sumit Mohan again.

MOHAN: Dialysis has a survival rate that is lower than most cancers at the five-year mark. So transplant is really the lifesaving opportunity for those individuals who have end-stage kidney disease. 

You heard Sumit right. A survival rate lower than most cancers. And the waiting list for donated kidneys has about 90,000 people on it. About 12 people on this list die every day. For kidney failure patients who are above the age of 60, nearly half die of them on the waiting list. And yet … 10 donated kidneys are discarded every day. Let me say this again: 12 people waiting for a kidney transplant die every day. But 10 kidneys donated by individuals who’ve recently died are thrown away every day.

So, what’s going on here? That brings us back to Sumit Mohan and his strange weekend of transplants. A kidney taken from a deceased donor can last about 24 to 36 hours. transplants are typically done the day after the organ is taken from the body. The spike in Saturday and Sunday transplants at Sumit’s hospital just meant that more kidneys had been harvested on Friday and Saturday. 

MOHAN: The first question it raised in our mind was wait, maybe it’s because there’s a lot more drunk driving on Fridays and Saturdays and more organs available from deceased donors. And that wasn’t the case.

All right, so let’s look at how a kidney from a dead body gets to someone who needs it. In order for a transplant to happen, the donor and recipient blood types, they have to match, and other factors also have to be compatible, like age for example. Some kidneys have problems that make them unusable for one patient but not for another. When doctors reject a kidney for their patient, it’s offered to the next one in line on the national waiting list. That process continues until someone says yes, at which point the kidney is urgently transported, sometimes across the country. And if no match is found in time, the kidney gets discarded. And it was this sequence of events that was funneling kidneys to Sumit’s hospital on weekends. 

MOHAN: In order for us to import organs from other parts of the country and transplant them over the weekend, that implied that other parts of the country were less willing to use these organs on the weekend.

Could that be true? Were hospitals more likely to reject kidneys on Fridays and Saturdays than on any other day of the week? And was this why Sumit and his colleagues at Columbia were getting more kidneys on weekends? To find out, Sumit first looked at how many rounds of rejection kidneys went through on different days of the week.

MOHAN: As you approach the weekend, the number of times a kidney gets turned down before it’s eventually accepted increases dramatically, suggesting that the phenomena that we’re seeing is a real one. 

They also looked at which days of the week had the most kidneys ending up in the trash. 

MOHAN: 20 percent more organs get thrown away on the weekend. If you match for organ quality, the organ quality is no different. And that was our first clue that there was something beyond organ quality that was influencing a decision by transplant centers as to whether to use a specific organ for a specific patient. 

These findings led to a troubling question: were usable kidneys being wasted? It was a difficult question to answer, and Sumit couldn’t figure out how to study it.

MOHAN: I had a nephrology fellow at the time, who came into the office one day and says, wait, I know what the solution to this question is.

Coming up: what the solution was, and what they found out. 

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Okay, back to Sumit. He was trying to figure out a way to uncover how many good kidneys, how many usable kidneys, were being thrown away. And one day, a physician training with him had the proverbial light bulb go off. He burst into Sumit’s office and said, “Everybody’s got two kidneys.” 

MOHAN: So you say, okay, everybody’s got two kidneys. We know that. What does that mean? And what he basically was implying was the idea that if everybody has two kidneys and we think the donor is a viable donor and we’ve gotten both kidneys, it’s certainly possible that one kidney got used because a transplant center said, yes, this is a viable kidney. Let’s use it. While the other kidney got turned down by multiple other transplant centers. And found its way into the trash. In that way, you have two kidneys that are perfectly matched, from a donor perspective. They’re the same age. They’ve been exposed to the exact same environment. The same medical conditions. 

It was a really interesting idea — trace the path of two kidneys taken from the same person to see how often one was transplanted and the other was tossed. If sometimes, one kidney was accepted because doctors thought it was usable and the other kidney was rejected, that might suggest that the kidney that was rejected was actually usable. But Sumit was still skeptical. How often could this possibly be happening? 

MOHAN: As mentors, we’re supposed to encourage our junior faculty and so I said, okay, let’s try it. I don’t expect to find anything, but let’s look. Right? 

Sumit and the fellow teamed up with colleagues at Columbia, Emory University, and the University of Texas. Using national records, they looked at kidney transplants from more than 88,000 deceased donors from 2000 through 2015. And once again, Sumit was surprised by what he found. 

MOHAN: We basically found almost 8,000 instances where you had a donor where one kidney got used and the other kidney, from that exact same donor, found its way into the trash.

So who got it right: the doctors who took the kidneys or the ones who rejected them? Well, the researchers looked at the reasons provided for each rejection. Sometimes, one kidney had problems that the other one didn’t have. It was damaged or abnormal. But turns out that those accounted for just a fraction of the discards. 

MOHAN: Centers that used the kidneys got it right. Those kidneys performed essentially as they would have been expected to. Their transplant recipients benefited from receiving those kidneys and went on to do as well as one would expect. Underscoring clearly that we don’t always get it right when we say we’re not using a kidney. 

So what’s the problem? Why do transplant centers reject good kidneys?

Alvin ROTH: Transplant centers are measured in a way that penalizes them for unsuccessful transplants, but doesn’t penalize them for transplants that they decide not to.

That’s Alvin Roth. He’s a professor of economics at Stanford University and the recipient of the 2012 Nobel Prize in Economics. His Nobel Prize was for work that included the design of a kidney exchange program for living kidney donors. It’s been incredibly successful at matching donors with recipients. 

ROTH: If you have a kidney that has an 85% chance of success, that might look like a life-saving opportunity to a patient, but it might look to a transplant center like risking censure you can’t have a 15% failure rate in the United States.

Transplant centers are kept under watch by the Scientific Registry of Transplant Recipients and also the Centers for Medicare and Medicaid Services. And according to their criteria, hospitals get dinged when their one-year survival rate after transplant surgery falls below 98 percent — in other words, they get penalized when fewer than 98 percent of the patients who received new kidneys at the hospital survive 12 months after the surgery., Sumit Mohan again.

MOHAN: Those centers that fall about a percent and a half below that? So about 96, 97 percent get flagged as underperforming transplant centers. And that’s important because patients who are on the transplant waitlist, who are on dialysis, have a 20 percent annualized mortality rate. So the survival rate for patients who are on dialysis compared to patients who have received a transplant is not really comparable. And that one and a half percent difference between an as expected performing transplant center versus an underperforming transplant center? While it may be statistically significant, it’s not clinically, meaningfully different. And that becomes part of the problem. Transplant centers are not incentivized to transplant their patients. 

And there’s a strange thing that’s missing from the criteria in this system. The powers that be … don’t seem to care about wasted kidneys. That’s not a thing that they even look at. Here’s Alvin Roth.

ROTH: A lot of kidneys are rejected by patients or on behalf of patients by their transplant centers that maybe we could use and the mortality rate on the waiting list is high. 

Now, the fact that we have more people on the waiting list and fewer kidneys from deceased donors isn’t necessarily bad news. 

ROTH: Partly it comes from greater success at keeping people alive while they’re waiting. It comes from a lower rate of mortality and traffic accidents in the United States. 

Keeping patients alive longer on the waitlist. Fewer car accidents. Those are good things. But, it’s still the case that with these long and large waitlists, perfectly good kidneys are being thrown away. Sumit and Al both have some pretty simple ideas about how to fix this. Sumit says a starting place for change could be the criteria used to measure transplant center performance. 

MOHAN: Today in the United States, depending on the transplant center a patient is wait-listed at their probability of getting a transplant in the first three years post waitlisting ranges from 4 percent to 64 percent. That’s an enormous amount of variation. If you live in New York City, you have access to nine transplant centers. The probability of transplantation varies across those nine transplant centers, seven-fold. It goes from 5 percent to 35 percent. So if you’re a patient getting on the waitlist, where would you want to go?

In other words, the national standards don’t necessarily represent what patients may want. A person facing death might be happier living five years with an imperfect kidney than living only five months on dialysis. And measuring quality by a one-year survival rate is also questionable. 

MOHAN: Patients don’t receive a transplant in the hope that they’re going to be alive in a year. They receive a transplant with the intention of living for many, many years. So that’s the first thing that we need to change. I think we need to change the timelines that we think about and what patients expect of us. 

That may mean that transplant centers need to loosen up a little or that our policies need to allow them to do that. As Al Roth points out, the U.S. could take a lesson from abroad. 

ROTH: Our French colleagues who do better at getting older, deceased donor kidneys. They think that we’re too risk-averse. 

A 2019 study in JAMA found that between 2004 and 2014, U.S. transplant centers turned their collective noses up at 28,000 deceased donor kidneys. French transplant centers would have taken 60 percent of those. Most of this difference was because the French were more willing to accept kidneys from older donors. But they were also less picky about donors who’d had hypertension or died from heart attacks.

ROTH: I think we could take more risks on behalf of our patients.

That leads to another issue: knowing the patient’s wishes in the first place. Sumit Mohan again.

MOHAN: When people turn down organs, they don’t share that information with patients. So there is no transparency in the system and no accountability. So if we want a policy solution here, the policy solution is that we increase accountability and we increase transparency. We should have shared decision-making where a transplant center is required to share information with their patients when there is an organ offer. Are they willing to accept a suboptimal organ because they’re having a miserable time on dialysis and they’ll do anything to get off it? Or are they doing just fine on dialysis and able to tolerate it really well and willing to wait it out for that much better kidney? We don’t know that if we don’t ask our patients. People come to very different conclusions of what they need and what they’re willing to endure. It’s not for us to assume those things. 

Sumit is trying to move his own hospital in this direction by researching a model for transplants based on shared decision-making. He’s currently awaiting funding for a study. Meanwhile, Al Roth sees a lot of potential to increase the number of kidneys transplanted from living donors. In particular, countries could collaborate a lot more.

ROTH: There are lots of barriers. We haven’t yet succeeded in coordinating with Canada, which is just crazy. You know, Canada is close. We fly kidneys around the United States. 

That does seem kind of crazy. A kidney that’s rejected in New York could be flown to California, but a kidney rejected in Winnipeg can’t be given to a dying patient in North Dakota, right across the border. As for kidney exchanges, the programs that connect organs donated by living people to appropriate patients, confining the network within a country’s borders makes no sense either. 

ROTH: It’s a global problem that requires a global solution. Which incidentally is something contrary to some of the medical orthodoxy. The World Health Organization believes that countries should be self-sufficient in organ transplantation. And that made some sense when there was only deceased donation and there aren’t enough deceased donors. But as soon as we start talking about kidney exchange, it makes sense to look at the whole world cause kidneys don’t know borders.

There’s another solution to consider. A big one. Reduce the number of people who need new kidneys in the first place. If you reduce the number of people who need kidney transplants, that’ll free up, or spare, those kidneys to be transplanted into other people who need them. 

Let’s think about how this plays out for a different organ: the liver. The most common reason for liver transplants in the U.S. is infection by the Hepatitis C virus. Hepatitis C kills nearly 300,000 people worldwide, each year. That’s in addition to people who die from liver disease due to other causes like obesity or alcohol use. 

A few years ago, drugs that cure patients of hepatitis C were developed. They are extraordinarily expensive, but they were also game-changers. Because if patients with hepatitis C were cured of their disease, they wouldn’t ultimately need liver transplants.

A study that my colleagues and I did found that proper screening and treatment for hepatitis C could spare more than 10,000 liver transplants over 20 years. We calculated that patients with liver failure not due to hepatitis C would have more than 7,000 extra livers at their disposal, and patients whose hepatitis C couldn’t be cured with the new drugs would have an additional 3,200 livers. 

This brings us back to kidneys. What if we get better at treating diabetes or high blood pressure, two leading causes of kidney failure? That could get a lot of people off the transplant list and free up kidneys for those who still need them. 

There’s one more possible avenue for shrinking the waitlist that’s making headlines lately: non-human, lab-grown kidneys. And this is actually happening. In late October, surgeons at New York University attached a kidney that was grown inside a pig to a patient who was brain dead and the kidney kept working. The pig had been genetically altered so that the kidney would not be rejected by a human. Transplanting kidneys grown inside of animals is still a long way from being common practice but this surgery marked a major scientific milestone. And, it turns out the problem Sumit and his colleagues found with tossing usable organs —it’s not just kidneys. 

MOHAN: We’ve looked at liver transplants and we’ve discovered the exact same phenomenon.

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There’s no doubt that huge strides have been made in kidney transplantation. Survival rates have improved dramatically over the past few decades, including among higher-risk patients. And the number of donations has been increasing too. But as these studies have made clear, we still have a long way to go. Too often, medical decision-making is not aligned to patients’ needs and wishes. Or as Al Roth puts it: 

ROTH: I can tell you about victory after victory in battles against kidney disease, but it’s in a war that we’re losing.

All right. That’s it for Freakonomics, M.D. this week. You can find links to all the studies we mentioned at Thanks for listening – we’re back for a whole new batch of episodes. It would be great if you could give us a review on Apple Podcasts or wherever you’re listening. It helps new people discover the show. And if you have any thoughts on the show, I’d really love to hear from you. You can email me at That’s B A P U at freakonomics dot com.

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Freakonomics, M.D. is part of the Freakonomics Radio Network, which also includes Freakonomics Radio, No Stupid Questions, and People I (Mostly) Admire. This show is produced by Stitcher and Renbud Radio. You can find us on Twitter and Instagram at @drbapupod. This episode was produced by Jessica Wapner and mixed by Eleanor Osborne. Original music composed by Luis Guerra. Our staff also includes Alison Craiglow, Greg Rippin, Tricia Bobeda, Emma Tyrrell, Lyric Bowditch, Jacob Clemente, and Stephen Dubner. If you like this show or any other show in the Freakonomics Radio Network, please recommend it to your family and friends. That’s the best way to support the podcasts you love. As always, thanks for listening. 

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  • Sumit Mohan, professor of medicine and epidemiology at Columbia University.
  • Alvin Roth, professor of economics at Stanford University.



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